In solid-vapor sorption reaction systems, a gaseous reactant is alternately absorbed and desorbed on a solid sorbent in one or more reaction chambers in a sorber or reactor. Where two reactors or banks of reactors are used, the system is operated in substantially opposing phases or half-cycles with one reactor or bank of reactors desorbing the gaseous reactant from the solid sorbent while the other reactor or bank of reactors is absorbing the gaseous reactant on the solid sorbent. The desorbed gaseous reactant or refrigerant vapor is directed to one or more condensers and after condensation is directed to one or more evaporators where it is vaporized. Heat may be recovered from the condenser and cooling from the evaporator. In other systems, reactors are used instead of condensers and evaporators for recovering energy from the refrigerant. Desorption is carried out by heating the solid sorbent, on which the gaseous reactant has been absorbed. Electric, steam, or gas-driven heaters are typically used for heating the solid sorbent, and/or heat transfer fluid is directed through a reactor heat exchanger to which the sorbent is thermally exposed. To initiate absorption a solid sorbent, from which the gaseous reactant or refrigerant has been desorbed, is cooled to a suitable temperature whereby it draws the gaseous refrigerant from the evaporator. The reactors may also be provided with heat exchangers and piping for directing heat transfer fluid between the reactors whereby heat released from an absorbing reactor is directed to a desorbing reactor to provide heating to carry out desorption. Such systems, apparatus and methods for their operation are well known in the art and are disclosed, for example, in U.S. Pat. Nos. 5,079,928, 5,263,330, 5,477,706, 5,598,721, and 5,628,205, all of which disclosures are incorporated herein by reference.
During a reaction cycle, an absorbing reactor is at a lower temperature than the desorbing reactor, i.e., the temperature of the solid sorbent and all other components within the desorbing reactor is higher than the temperature of the solid sorbent and all other components in the absorbing reactor. At the end of a half-cycle, with a majority of gaseous reactant desorbed from the sorbent in the desorbing reactor and a majority of gaseous reactant absorbed on the sorbent in the absorbing reactor, the absorption/desorption phases are reversed. At this half-point of the cycle, the desorbing reactor must be cooled and the absorbing reactor must be heated. At least partial heating of the desorbing reactor may be supplied by directing heat of absorption from the absorbing reactor, in the previous half-cycle, to the desorbing reactor, such as disclosed in the aforesaid patents. Cooling of the absorbing reactor may be accomplished utilizing a portion of the condensed refrigerant to the heat exchange section of the absorbing reactor. Such cooling may be assisted by utilizing vaporized heat transfer fluid or refrigerant for driving the liquid heat transfer fluid or refrigerant in the cooling: loop, such as disclosed in U.S. Pat. No. 5,477,706. However, because of the substantial differential temperature between the higher temperature desorbing reactor and the lower temperature absorbing reactor, at the end of the half-cycle, substantial energy is required to elevate the temperature of the reactor in which absorption has just been completed sufficiently to initiate desorption. This energy requirement substantially penalizes the overall efficiency of the system and requires hardware and components such as heaters, thermostats, piping, heat exchangers, multiple condensers or condenser sections, etc. to effectively and rapidly switch the reactor half-cycles. Such components significantly increase the cost and size of the sorption systems.
The present invention comprises a method and apparatus for providing recuperation between two opposing sorbers or opposing banks of sorbers in a single or multiple-stage solid-vapor sorption system utilizing the sorption energy that exists between the reactors. The method utilizes a mass-fraction of remaining absorbed vapor on the sorbent in the desorbing reactor near the completion of a half-cycle, prior to reversing the phases. The method is carried out by utilizing piping between the reaction chambers of the opposing reactors and one or more valves for opening and closing the pipe or pipes whereby the timing of the recuperation may be selected and controlled to achieve the desired energy transfer.